Evolution in African Marantaceae - Evidence from Phylogenetic, Ecological and Morphological Studies

The Marantaceae (similar to 530 spp.) are one of the most species rich families within the order Zingiberales which incites the search for evolutionary factors favoring speciation. A positive influence on their divergence is ascribed to their unique explosive pollination mechanism which has been proposed to be a key innovation. To test this hypothesis phylogenies of the two major African clades (Sarcophrynium and the Marantochlon clade) were established based on data from nuclear (ITS, 5S) and chloroplast (trnL/trnL-F) DNA for an almost complete taxon sample. The phylogeny was used to parsimoniously reconstruct morphological and ecological traits and geographic distribution patterns. The resulting molecular relationships of the genera are congruent with the existing family phylogeny. As in previous studies the species Atnenidia conferta is nested within Marantochlon so that a new circumscription of Marantochlon is proposed leading to the new name Marantochloa conferta. Hybridization events, adaptation to different pollinators, and Pleistocene climatic fluctuations are hypothesized evolutionary factors fostering speciation in the African clades. The explosive pollination mechanism might have played an important role in optimizing the mating system but did certainly not force speciation directly through mechanisms of reproductive isolation.